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No description available.

No description available.

The effect of sub-lethal chlorine stress on various strains/serotypes of Salmonella on biofilm formation and thermal resistance was studied. The effect of oxidative stress (induced by 150 ppm of chlorine in TSB) on Salmonella biofilm formation on polystyrene and stainless steel surfaces at three temperatures (4°C, 30°C, and room temperature) in nutrient rich (full strength TSB) and nutrient limited conditions (1/10th TSB) was evaluated. On polystyrene surface, chlorine stressed S. Heidelberg (strain ID 72), S. Newport (strain ID 107) and S. Typhimurium (ATCC 14028) formed stronger (P < 0.05) biofilms at 30°C. On stainless steel, the chlorine stressed S. Heidelberg (ATCC 8326) and S. Enteritidis (ATCC 4931) at room temperature formed stronger (P < 0.05) biofilms as compared to the non-stressed control cells. The thermal resistance of short-term (1h) and long-term (27d) chlorine stressed Salmonella Heidelberg and S. Typhimurium were compared with the non-stressed controls at three different temperatures (55°C, 58°C and 61°C) and two growth phases (logarithmic and stationary). The short-term stressed log phase cells (both serotypes) were found to be more sensitive (P< 0.05) to thermal inactivation in TSB. Upon long-term sub-lethal chlorine exposure, Salmonella developed a rugose morphotype on tryptic soy agar at 37°C. The rugose morphotype provided significant thermal protection (P< 0.05) against heat stress as compared to smooth morphotype. In chicken broth, at 55°C, short-term chlorine stressed stationary phase S. Typhimurium displayed a higher D55 value compared to non-stressed cells. The findings from this research reveal that some Salmonella strains have the potential to form stronger biofilms and exhibit higher thermal tolerance upon exposure to sub-lethal chlorine concentration.

För att hålla vattendragen och miljön rena, renas avloppsvattnet för att nå ett visst mått innan det släpps ut. Vi gjorde en fallstudie för att utvärdera metoderna som används för att behandla avloppsvatten i tre steg: primär, sekundär och tertiär i delstaten Texas, USA. Vi fann att olika fysikaliska, kemiska och biologiska bearbetningsmetoder används i stor utsträckning i dessa tre stadier. Även om en del av det slam som produceras i en avloppsvattenreningsanläggning utsätts för anaerob rötning (AD) process för att producera biogas, skickas majoriteten av dem till deponier som är ohållbart eftersom det skapar miljöföroreningar som läckage av näringsämnen, påverkar markens biologiska mångfald och släpper ut giftiga gaser och växthusgaser (GHG) som CH4, CO2, N2O. Den mest hållbara och prisvärda metoden för att behandla avloppsvatten är att använda mikroalger och några av fördelarna inkluderar: (i) använda CO2 som en kolkälla och generera syre, (ii) synergistiskt arbeta med aeroba bakterier som bryter ner organiska föroreningar i vatten på kort tid tid, (iii) högeffektiv bindning av överskott av kväve, fosfor och tungmetaller i avloppsvatten. Flera algbaserade reningsmetoder för avloppsvatten har utvecklats. Bland dem är reaktorn Rotating Algal Biofilm (RAB) en av de ledande behandlingsmetoderna som använder ett roterande band som består av syntetiska material som rör sig på en cylinder som är delvis nedsänkt i avloppsvatten. Algbiomassan kunde skördas från bältet genom att helt enkelt skrapa materialets yta. Vi uppskattade att ~1793,7 miljoner liter avloppsvatten behandlas dagligen i delstaten Texas och hypotetiskt om allt avloppsvatten behandlas med RAB skulle ~174,2 ton algbiomassa kunna produceras. Denna algbiomassa kan användas för AD-processen eller vidarebearbetas och fraktioneras till lipider, kolhydrater och proteiner med hjälp av etablerade hydrotermiska bearbetningsmetoder och användas som byggstenar för att producera bränslen, kemikalier och biomaterial. Tre scenarier har undersökts som belyser potentialen och fördelarna med att använda alger för att behandla avloppsvatten jämfört med konventionella metoder för avloppsvattenrening och hur denna övergång kommer att gynna ekonomin och miljön. / To keep the waterways and environment clean, wastewater is treated to reach a certain metric before they are discharged.  We did a case study to evaluate the methods used to treat wastewater in three stages: primary, secondary, and tertiary in the state of Texas, United States. We found different physical, chemical, and biological processing methods are widely used in these three stages. Though some of the sludge produced in a wastewater treatment facility are subjected to anaerobic digestion (AD) process to produce biogas, the majority of them are sent to landfills which is unsustainable as it creates environmental pollution such as nutrient leaching, impacts soil biodiversity, and releases toxic gases and greenhouse gases (GHGs) such as CH4, CO2, N2O. The most sustainable and affordable method of treating wastewater is using microalgae and some of the advantages include: (i) use CO2 as a carbon source and generate oxygen, (ii) synergistically working with aerobic bacteria breaking down organic contaminants in water in a short period of time, (iii) highly efficient sequester of excess nitrogen, phosphorus, and heavy metals in wastewater. Several algal based wastewater treatment methods have been developed. Among them, the Rotating Algal Biofilm (RAB) reactor is one of the leading treatment methods that uses a rotating belt made up of synthetic materials moving on a cylinder partially submerged in wastewater. The algal biomass could be harvested from the belt by simply scrapping the material's surface. We estimated that ~1793.7 million gallons of wastewater are treated daily in the state of Texas and hypothetically if all the wastewater is treated using RAB ~174.2 tons of algal biomass could be produced. This algal biomass can be used for the AD process or further processed and fractionated to lipids, carbohydrates, and proteins using established hydrothermal processing methods and used as building blocks for producing fuels, chemicals, and biomaterials. Three scenarios have been investigated, highlighting the potential and benefits of using algae to treat wastewater compared to conventional wastewater treatment methods and how this transition will benefit the economy and environment.

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Anaerobic digestion (AD) is a widespread technology for treating waste streams such as livestock manure. During AD, biogas is produced and subsequently used as renewable energy for certain purposes, such as injection into the natural gas grid or as fuel for transportation. Despite its many advantages, AD can be limited by various factors, including process instability against volatile fatty acids (VFA), nitrogen overloads, or the presence of inhibitors, as well as the need for biogas post-processing to increase its methane content. Therefore, strategies are needed to monitor the AD process, control the effluent quality and upgrade the biogas recovered. Microbial electrochemical technologies (MET) have the potential to optimize AD. MET are systems in which oxidation and/or reduction reactions are catalyzed by electroactive microorganisms (EAM) on the surface of an electrode. Typically, EAM used in AD-MET combinations are dominated by Geobacter spp., that form multilayer biofilms on electrodes (e.g., anodes) used as solid terminal electron acceptors. However, using Geobacter spp. dominated biofilm anodes in AD-MET combinations has so far encountered several hurdles, ranging from biofilm dispersal to inhibition of biofilm performance. Thus, the intention of the present thesis was to identify and to address the different inhibition processes of Geobacter spp. dominated biofilm anodes in AD-MET combinations. Particular attention was devoted to the impact that planktonic methanogens, particles and dissolved components present in AD effluents may have on the activity, stability and microbial community of Geobacter spp. dominated biofilm anodes. This was achieved by investigating the effect of biofilm age, applied anode potentials as well as the role played by specific methanogens with different metabolisms on the activity, stability and microbial community of Geobacter spp. dominated biofilms. The results indicated that older Geobacter spp. dominated biofilm anodes (≥ 5-week-old) are far more active and stable than younger biofilms (≤ 3-week-old) in AD environments. Compared to high applied anode potential (0.4 V vs. Ag/AgCl sat. KCl), low applied anode potentials (-0.2 V to 0.2 V vs. Ag/AgCl sat. KCl) resulted in higher activities of Geobacter spp. dominated biofilm anodes in AD environments. Other results indicated that AD effluents dominated by strict acetoclastic methanogens (e.g., Methanothrix spp.) cause deterioration in biofilm stability and activity, in contrast to AD effluents dominated by hydrogenotrophic methanogens (e.g., Methanobacterium spp.). In conclusion, the thesis provides useful information for understanding and improving the performance of AD-MET combinations and ways to overcome the multiple hurdles encountered so far.:1 Introduction 12 1.1 Basics of microbiology of anaerobic digestion 12 1.1.1 Methanogens and their functionality 12 1.1.2 Anaerobic digestion - methanogens and bacteria 13 1.1.3 Microbial diversity in anaerobic digestion: focus on methanogens 14 1.1.4 Metabolism and syntrophy in anaerobic digestion 16 1.1.5 Parameters influencing anaerobic digestion 18 1.2 Microbial electrochemical technologies 19 1.2.1 Primary microbial electrochemical technologies - possible applications 19 1.2.2 Basic examples of primary microbial electrochemical technologies 21 1.2.3 Geobacter spp. as model electroactive microorganism in microbial electrochemical technologies 23 1.2.4 Modes of electron transfer between electroactive microorganisms and electrodes 24 1.2.5 Electrochemical characterization of biofilm anodes 27 1.3 Combination of anaerobic digestion and microbial electrochemical technologies 28 1.3.1 Benefits: biotechnological applications 28 1.3.2 Challenges: factors limiting the combination anaerobic digestion - microbial electrochemical technologies 29 1.4 Aims and thesis outline 30 2 Publication 1: Benefits of Age – Improved Resistance of Mature Electroactive Biofilm Anodes in Anaerobic Digestion 33 2.1 Supplementary information for “Benefits of Age – Improved Resistance of Mature Electroactive Biofilm Anodes in Anaerobic Digestion” 43 3 Publication 2: Combining Geobacter spp. dominated biofilms and anaerobic digestion effluents - the effect of effluent composition and electrode potential on biofilm activity and stability 55 3.1 Supplementary information for “Combining Geobacter spp. dominated biofilms and anaerobic digestion effluents - the effect of effluent composition and electrode potential on biofilm activity and stability” 67 4 Publication 3: A unified and simple medium for growing model methanogens 91 4.1 Supplementary information for “A unified and simple medium for growing model methanogens” 105 5 Publication 4: Effect of model methanogens on the activity, stability, and microbial community structure of Geobacter spp. dominated biofilm anodes 117 5.1 Supplementary information for “Effect of model methanogens on the activity, stability, and microbial community structure of Geobacter spp. dominated biofilm anodes” 153 6 Discussion 167 6.1 The older the biofilm, the higher its activity and resistance when combined with anaerobic digestion effluents 167 6.2 Low applied anode potential leads to high activity of Geobacter spp. dominated biofilm in anaerobic digestion environments. 168 6.3 The role of methanogens, abiotic particles, dissolved components in the combination anaerobic digestion – microbial electrochemical technologies 170 6.3.1 Abiotic particles, dissolved components present in anaerobic digestion effluents do not always interfere with the activity, stability and community of Geobacter spp. dominated biofilm anodes 170 6.3.2 The activity and community of Geobacter spp. dominated biofilm anodes in anaerobic digestion environments vary with the predominant group of methanogens 171 7 Conclusions and future prospects 173 8 References 176 9 Appendix 187 9.1 Author contribution statements of published articles 187 9.2 Curriculum vitae 193 9.3 List of publications and conference contributions 196 9.4 Acknowledgment 199 9.5 Declaration of authorship 201

Colonization is prerequisite for infection and transmission of Streptococcus pneumoniae, or pneumococcus. Currently available pneumococcal conjugate and pneumococcal polysaccharide vaccines can provide protection against a limited number of capsular serotypes. Implementation of vaccines has decreased the frequency of invasive pneumococcal disease and their colonization rates, but only in a serotype-dependent manner. This has led to serotype replacement in pneumococcal ecology and increased invasive disease caused by non-vaccine serotypes. Development of conserved protein-based vaccine that can provide protection against all pneumococcal serotypes is needed. Numerous surface proteins are conserved in all serotypes, and some are known to be involved in the colonization process. Understanding how pneumococcal surface proteins interact with host cells and determining their roles in colonization will aid in vaccine development. In this dissertation, we characterized host cell receptors of pneumococcal surface proteins, and proteins involved in biofilm formation, and their effect in colonization. We utilized a novel protein expression vector, pOS1, which can express secreted proteins with no LPS, IPTG induction, or cell lysis requirement. These expressed recombinant proteins were used for further investigation. We identified that human Annexin A2 (ANXA2) interacts with pneumococcal surface adhesion A (PsaA) protein. ANXA2 transduced cells showed significant increase in binding with pneumococcus compared to non-transduced cells. We conducted proteomic profiling of planktonic and biofilm membrane proteins and identified that two lipoproteins (AmiA, SP_0148) were overexpressed during biofilm formation. Isogenic mutants lacking these individual proteins showed decreased in biofilm formation compared to their parental strain. Deletion of SP_0148 led to decreased adhesion of pneumococcus to human nasopharyngeal epithelial cells (Detroit 562). These results increased our understanding of pneumococcal surface proteins involved in biofilm-formation and colonization as well as identifying new host receptors ligands for these adhesins.

La résistance aux antibiotiques est responsable de nombreuses maladies et décès depuis plusieurs décennies. L'augmentation de la résistance bactérienne a donc encouragé les chercheurs à développer de nouveaux antibiotiques, et de nouvelles stratégies pour contrer les différents mécanismes de résistance. L'un des mécanismes de résistance les plus notables est la formation de biofilms. Par conséquent, notre groupe de recherche s'est concentré sur différents types de mécanismes d'action des antibiotiques, plus particulièrement sur la perméabilisation de la membrane cellulaire. Ceci est réalisé par la formation de pores, d'agrégats, de canaux ou de micelles à travers celle-ci. En réponse à cela, nous avons synthétisé des composés antibactériens possédant deux cations benzimidazolium, deux chaînes apolaires hydrophobes et un échafaudage phényl- ou pyridyl-phényléthynylène, ayant la capacité de former des agrégats supramoléculaires via des interactions π-π et des liaisons hydrogène à travers la bicouche lipidique. Ces composés perturbateurs de la membrane agissent par un mécanisme rapide et efficace et ont montré de bons résultats contre les souches MRSA (Methicilin Resistant Staphylococcus Aureus), ce qui en fait des candidats prometteurs pour combattre les infections bactériennes et la formation des biofilms. / Antibiotic resistance has been responsible for multiple diseases and deaths for several decades. The rise of bacterial resistance has therefore encouraged researchers to develop new antibiotics, and new strategies to counter their various resistance mechanisms. One of the more notable resistance mechanics is the formation of biofilms. Consequently, our research group focused on the different types of antibiotics mechanisms of action, more particularly on the permeabilization of the cell membrane. This is achieved through the formation of pores, aggregate, channels, or micelles through it. In response to this, we have thus synthesized antibacterial compounds with a benzimidazolium cation, a hydrophobic apolar chain and a phenyl- or pyridyl-phenylethynylene scaffold with the capacity to form supramolecular aggregates via π-π interaction and hydrogen bonding through the lipid bilayer. These membrane-disrupting compounds act via a rapid and effective mechanism and have shown good results against strains of MRSA, thus making promising candidates to combat bacterial infections and biofilms formation.